Tag: Space Weather

The Earth and Mars are currently on exact opposite sides of the sun — a celestial situation known as “Mars solar conjunction” — a time when we have no way of directly communicating with satellites and rovers at the Red Planet. So, when the Solar and Heliospheric Observatory (SoHO) spotted a huge (and I mean HUGE) bubble of superheated plasma expand from the solar disk earlier today (July 23), it either meant our nearest star had launched a vast coronal mass ejection directly at Earth or it had sent a CME in the exact opposite direction.

As another solar observatory — the STEREO-A spacecraft — currently has a partial view of the other side of the sun (it orbits ahead of Earth’s orbit, so it can see regions of the sun that are out of view from our perspective), we know that this CME didn’t emanate from the sun’s near side, it was actually launched away from us and Mars will be in for some choppy space weather very soon.

It appears the CME emanated from active region (AR) 2665, a region of intense magnetic activity exhibiting a large sunspot.

CMEs are magnetic bubbles of solar plasma that are ejected at high speed into interplanetary space following a magnetic eruption in the lower corona (the sun’s lower atmosphere). From STEREO-A’s unique vantage point, it appears the CME detected by SoHO was triggered by a powerful solar flare that generated a flash of extreme-ultraviolet radiation (possibly even generating X-rays):

Observation by STEREO-A of the flaring event that likely triggered today’s CME (NASA/STEREO)

When CMEs encounter Earth’s global magnetic field, the radiation environment surrounding our planet increases, posing a hazard for satellites and unprotected astronauts. In addition, if the conditions are right, geomagnetic storms may commence, creating bright aurorae at high latitudes. These storms can overload power grids on the ground, triggering mass blackouts. Predicting when these storms will occur is of paramount importance, so spacecraft such as SoHO, STEREO and others are constantly monitoring our star’s magnetic activity deep inside the corona and throughout the heliosphere.

Mars, however, is a very different beast to Earth in that it doesn’t have a strong global magnetosphere to shield against incoming energetic particles from the sun, which the incoming CME will be delivering very soon. As it lacks a magnetic field, this CME will continue to erode the planet’s thin atmosphere, stripping some of the gases into space. Eons of space weather erosion has removed most of the Martian atmosphere, whereas Earth’s magnetism keeps our atmospheric gases nicely contained.

When NASA and other space agencies check in with their Mars robots after Mars solar conjunction, it will be interesting to see if any recorded the space weather impacts of this particular CME.

As the sun dips into extremely low levels of activity before the current cycle’s “solar minimum”, a vast coronal hole has opened up in the sun’s lower atmosphere, sending a stream of fast-moving plasma our way.

To the untrained eye, this observation of the lower corona — the sun’s magnetically-dominated multi-million degree atmosphere — may look pretty dramatic. Like a vast rip in the sun’s disk, this particular coronal hole represents a huge region of “open” magnetic field lines reaching out into the solar system. Like a firehose, this open region is blasting the so-called fast solar wind in our direction and it could mean some choppy space weather is on the way.

As imaged by NASA’s Solar Dynamics Observatory today, this particular observation is sensitive to extreme ultraviolet radiation at a wavelength of 193 (19.3 nanometers) — the typical emission from a very ionized form of iron (iron-12, or FeXII) at a temperature of a million degrees Kelvin. In coronal holes, it looks as if there is little to no plasma at that temperature present, but that’s not the case; it’s just very rarefied as it’s traveling at tremendous speed and escaping into space.

The brighter regions represent closed field lines, basically big loops of magnetism that traps plasma at high density. Regions of close fieldlines cover the sun and coronal loops are known to contain hot plasma being energized by coronal heating processes.

When a coronal hole such as this rotates into view, we know that a stream of high-speed plasma is on the way and, in a few days, could have some interesting effects on Earth’s geomagnetic field. This same coronal hole made an appearance when it last rotated around the sun, generating some nice high-latitude auroras. Spaceweather.com predicts that the next stream will reach our planet on March 28th or 29th, potentially culminating in a “moderately strong” G2-class geomagnetic storm. The onset of geomagnetic storms can generate impressive auroral displays at high latitudes. Although not as dramatic as an Earth-directed coronal mass ejection or solar flare, the radiation environment in Earth orbit will no doubt increase.

The sun as seen right now by the SDO’s HMI instrument (NASA/SDO)

The sun is currently in a downward trend in activity and is expected to reach “solar minimum” by around 2019. As expected, sunspot numbers are decreasing steadily, meaning the internal magnetic dynamo of our nearest star is starting to ebb, reducing the likelihood of explosive events like flares and CMEs. This is all part of the natural 11-year cycle of our sun and, though activity is slowly ratcheting down its levels of activity, there’s still plenty of space weather action going on.

Last week, amateur astronomer Wayne Jaeschke noticed something peculiar in his observations of Mars — there appeared to be a cloud-like structure hanging above the limb of the planet.

Many theories have been put forward as to what the phenomenon could be — high altitude cloud? Dust storm? An asteroid impact plume?! — but it’s all conjecture until we can get follow-up observations. It is hoped that NASA’s Mars Odyssey satellite might be able to slew around and get a close-up view. However, it appears to be a transient event that is decreasing in size, so follow-up observations may not be possible.

For the moment, it’s looking very likely that it is some kind of short-lived atmospheric feature, and if I had to put money on it, I’d probably edge more toward the mundane — like a high-altitude cloud formation.

Despite the lack of a global magnetic field like Earth’s magnetosphere, Mars does have small pockets of magnetism over its surface. When solar wind particles collide with the Earth’s magnetosphere, highly energetic particles are channeled to the poles and impact the high altitude atmosphere — aurorae are the result. On Mars, however, it’s different. Though the planet may not experience the intense “auroral oval” like its terrestrial counterpart, when the conditions are right, solar particles my hit these small pockets of magnetism. The result? Auroral umbrellas.

The physics is fairly straight forward — the discreet magnetic pockets act as bubbles, directing the charged solar particles around them in an umbrella fashion. There is limited observational evidence for these space weather features, but they should be possible.

As the sun is going through a period of unrest, amplifying the ferocity of solar storms, popping off coronal mass ejections (CMEs) and solar flares, could the cloud-like feature seen in Jaeschke’s photograph be a bright auroral umbrella? I’m additionally curious as a magnetic feature like this would be rooted in the planet’s crust and would move with the rotation of the planet. It would also be a transient event — much like an atmospheric phenomenon.

The physics may sound plausible, but it would be interesting to see what amateur astronomers think. Could such a feature appear in Mars observations?

This morning, at 08:55 UT, NASA’s Solar Dynamics Observatory (SDO) detected a C3-class flare erupt inside a sunspot cluster. 100,000 kilometers away, deep within the solar atmosphere (the corona), an extended magnetic field filled with cool plasma forming a dark ribbon across the face of the sun (a feature known as a “filament”) erupted at the exact same time.

It seems very likely that both events were connected after a powerful shock wave produced by the flare destabilized the filament, causing the eruption.

A second solar observatory, the Solar and Heliospheric Observatory (SOHO), then spotted a huge coronal mass ejection (CME) blast into space, straight in the direction of Earth. Solar physicists have calculated that this magnetic bubble filled with energetic particles should hit Earth on August 3, so look out for some intense aurorae, a solar storm is on its way…

Predicting space weather is not for the faint-hearted. Although the Sun appears to have a predictable and regular cycle of activity, the details are a lot more complex. So complex in fact, that the world’s greatest research institutions have to use the most powerful supercomputers on the planet to simulate the most basic of solar dynamics. Once we have a handle on how the Sun’s interior is driven, we can start making predictions about how the solar surface may look and act in the future. Space weather prediction requires a sophisticated understanding of the Sun, but even the best models are flawed.

Today, another solar cycle prediction has been released by the guys that brought us the “$2 trillion-worth of global damage if a solar storm hits us” valuation earlier this month. According to NOAA scientists sponsored by NASA, Solar Cycle 24 will peak in May 2013 with a below-average number of sunspots.

“If our prediction is correct, Solar Cycle 24 will have a peak sunspot number of 90, the lowest of any cycle since 1928 when Solar Cycle 16 peaked at 78,” says Doug Biesecker of the NOAA Space Weather Prediction Center.

Although this may be considered to be a “weak” solar maximum, the Sun still has the potential to generate some impressive flares and coronal mass ejections (CMEs). Although I doubt we’ll see the record-breaking flares we saw in 2003 (pictured top), we might be hit by some impressive solar storms and auroral activity will certainly increase in Polar Regions. But just because the Sun will be more active, it doesn’t mean we will be struck by any big CMEs; space is a big place, we’d be (un)lucky to be staring directly down the solar flare barrel.

So, we have a new prediction and the solar models have been modified accordingly, but it is hard to understand why such tight constraints are being put on the time of solar maximum peak (one month in 2013) and the number of sunspots expected (90, or thereabouts). Yes, sunspot activity is increasing, but we are still seeing high-latitude sunspots from the previous cycle (Solar Cycle 23) pop up every now and again. This is normal, an overlap in cycles do occur, yet it surprises me that any definitive figures are being placed on a solar maximum that may or may not peak four years from now.

Tenuous link: Are you really happy with that prediction? (NOAA/NASA)

We are able to look at the history of sunspot number and we can see the cycles wax and wane, and we can pick out a cycle that most resembles the one we are going through now, but that doesn’t mean that particular cycle will happen this time around. Statistically-speaking, there’s a higher chance of a similar-looking cycle from the past happening in this 24th cycle, but predictions based on this premise are iffy to say the least.

“It turns out that none of our models were totally correct,” says Dean Pesnell of the Goddard Space Flight Center, NASA’s lead representative on the panel. “The sun is behaving in an unexpected and very interesting way.”

Personally, I think we should concentrate less on predicting when or how the next solar maximum presents itself. Solar models are not going to suddenly predict the nature of the solar cycle any more than we can predict terrestrial weather systems more than a few days in advance.

Using the atmospheric weather analogy, we know the seasons cycle as the year goes on, but there is no way we can say with any degree of certainty when the hottest day of the year is going to be, or which week will yield the most rain.

The same goes for our Sun. It is vastly complex and chaotic, a system we are only just beginning to understand. We need more observatories and more solar missions with advanced optics and spectrometers (and therefore a huge injection of funding, something solar physicists have always struggled without). Even then, I strongly doubt we’ll be able to predict exactly when the peak of the solar cycle is going to occur.

That said, space weather prediction is a very important science, but long-term forecasts don’t seem to be working, why keep on releasing new forecasts when the old one was based on the same physics anyway? Predicting an inactive, active or mediocre solar maximum only seems to cause alarm (although it is a great means to keep solar physics in the headlines, which is no bad thing in my books).

I suppose if you make enough predictions, eventually one will be correct in four years time. Perhaps there will be a peak of 90 sunspots by May 2013, who knows?

If you’re blindfolded, spun around and armed with an infinite supply of darts, you’ll eventually hit the board. Hell, you’ll probably even hit the bullseye…

Source: NASA, special thanks to Jamie Rich for bringing this subject to my attention!

Sigmoids in the solar corona have been studied for many years, but little explanation of their formation or why they are often the seed of powerful solar flares have been forthcoming. Using high-resolution X-ray images from the Japanese-led solar mission Hinode (originally Solar-B), solar physicists have known that these very hot S-shaped structures are composed of many highly stressed magnetic flux tubes filled with energized plasma (also known as ‘fibrils’), but until now, little was known about the formation and flare eruption processes that occur in sigmoids.

Now, a team of solar physicists from the University of St Andrews believe they have found an answer using powerful magnetohydrodynamic (MHD) computer models, aiding our understanding of coronal dynamics and getting us one step closer to forecasting space weather…Continue reading “An Explanation For Solar Sigmoids”